The Grumman Hellcat F Mk. I was an American single seat monoplane fighter aircraft. Hellcat F Mk. I was the British designation for the F6F-3. It currently sits as a Tier 3 Premium plane in the British line, with a cost of 1150 . The Hellcat, when used, provides a 140% reward rate and a 100% experience bonus.

A single-seat, single-engine, all-metal cantilever monoplane fighter with an enclosed cockpit and a retractable landing gear system. It was designed by the design office of Grumman Aircraft Engineering Corporation under the direction of Leroy Grumman and William Schwendler. A prototype of the XF6F-1 fighter made its first flight on 26 July 1942. In October 1942, the first production version, F6F-3, was launched.

The aircraft was equipped with a 2,000 hp Pratt & Whitney R-2800-10 Double Wasp double-row, eighteen-cylinder, radial air-cooled engine and a Hamilton Standard three-bladed propeller. Its armament consisted of six 12.7 mm Colt-Browning M2.5 machine guns, with 400 rounds each, located in the wings. Bomb racks under the fuselage and under the wings could carry up to three bombs weighing up to 1,000 lb (454 kg), six 127 mm HVARs, or two 298 mm Tiny Tim anti-ship unguided rockets. An external fuel tank could be mounted under the central bomb rack.
The aircraft was equipped with an arresting hook, and the wing panels could be folded up over themselves.

The F6F-3 entered service with the USN in January 1943, and later, in July of the same year, the planes began to be delivered to Great Britain under the Lend-Lease Act. In the British FAA, the aircraft initially received the designation of Grumman Gannet Mk.I, but it was later changed to the Hellcat F Mk.I.

Beginning in December 1943, Hellcats included in the Royal Navy's aviation force were assigned to accompany convoys across the Atlantic Ocean. In March 1944, units equipped with these aircraft participated in raids on the anchorage of the German battleship Tirpitz in Norway. From June 1944 on, British Hellcats fought in the Mediterranean theater and near the beaches of Normandy. They were launched in large numbers from the aircraft carriers of the British Pacific Fleet in the Far East. British naval pilots on Hellcat fighters won a combined total of 52 victories.

A total of 1,320 Hellcat fighters were delivered to Great Britain and withdrawn from service in August 1946.